[libc] Add new libc

This new libc is mostly from scratch, with *printf() functions provided
by Marco Paland and Eyal Rozenberg's tiny printf library, and malloc and
friends provided by dlmalloc.

src/libraries/libc/string/strncmp.cpp

@@ -0,0 +1,25 @@
+/** \file memcpy.cpp
+  *
+  * This file is part of the C standard library for the jsix operating
+  * system.
+  *
+  * This Source Code Form is subject to the terms of the Mozilla Public
+  * License, v. 2.0. If a copy of the MPL was not distributed with this
+  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+  */
+
+#include <string.h>
+
+int strncmp(const char *s1, const char *s2, size_t n) {
+    if (!s1 || !s2) return 0;
+
+    char const * c1 = s1;
+    char const * c2 = s2;
+
+    while (n && *c1 && *c2 && *c1++ == *c2++) n--;
+
+    if (!n || *c1 == *c2) return 0;
+    if (!*c2 || *c1 > *c2) return 1;
+    return -1;
+}
+